Something like
add_filter('acf/update_value/type=gallery', 'remove_gallery_images', 10, 3);
function remove_gallery_images($value, $post_id, $field) {
$images_to_delete = array();
$old_value = get_field($field['name'], $post_id, false);
if (!is_array($old_value)) {
return $value;
}
if (!$value) {
$images_to_delete = $old_value;
} else {
foreach ($old_value as $image_id) {
if (!in_array($image_id, $value)) {
$images_to_delete[] = $image_id;
}
}
}
if (count($images_to_delete)) {
foreach ($images_to_delete as $image_id) {
wp_delete_attachment($image_id, true);
}
}
return $value;
}
but you should be sure that only images that are uploaded to posts can be added to galleries.
Also, when someone is editing content and creates a standard WP gallery, as well as adding images to content and and then having them deleted by one of these functions you’ll get errors in other areas of your site. Hopefully the person that gave you that code warned you about this.
